Reed It and Reap
Reed It and Reap
Mimi Cavender
Morning on the Blanco. Let’s walk upstream along a little stretch of River Road just west of Wimberley, Texas. Another late September dawn slowly brightens what little water still pools in wide shallows, riffles over corrugated limestone riverbed, and squeezes through a last narrow channel under the far bank.
After a year’s drought, new vegetation crowds in where once was water. Tall prairie grasses, willows, sycamore saplings—an abundance of native species—populate all this extra dry land. But one enthusiastic new resident needs eviction. Walk with me, and we’ll take a look.
This drought-crippled stream is the same Blanco that recently lost trees, homes, and people in a tragic flood. Now after seven years, many tears, federal money, and a thousand volunteers, recovery of this beautiful river course is on its hundred-year track. The banks are stabilized, new-planted Bald Cypress, Cedar Elm, and Sycamore are thriving. Even the shattered old cypress snags are pushing new growth.
In Texas, landowners are stewards of 96% of the land and of the water on and under it. Some of the folks along the Blanco still mow the river bank. Most make the wiser choice to encourage its more resilient natural state. With us—and without us—nature finds a way.
Competing with dense native prairie grasses, invasive Johnsongrass may stay controlled.
Even browned out, roadside native grass cultures stabilize a steep bank. If you mow, it should be in spring, well after seed dispersal.
Mustang Grape overtakes a slow-growing Cedar Elm. Stripping it out before its shade kills the young tree might be a good idea. Look for more vines just starting before they engulf these precious riverside trees.
Texas Virgin’s Bower, a native Clematis also called Old Man’s Beard, glows in the morning sun.
We’re walking upstream on dry limestone. It’s clean-scoured Blanco river bottom from times of high stream flow.
As the riffling water shallows out to drought levels only inches deep, we spot the reason for our hike. It’s non-native and very invasive Arundo donax—Giant Reed—fixin’ to bloom. No, folks, it’s not Giant River Cane—that’s Arundaria gigantea, North America’s only native bamboo, growing in higher, slightly drier environments. This giant reed—call it by its name: Arundo—grows to 30 feet tall at water’s edge or inside shallow river courses. Both giant river cane and this monster reed, Arundo, quickly form almost unstoppable deep-rhizomed monocultures. But we’re concerned here—no, we should be passionately proactive here—about Arundo.
Pretty, isn’t it? I’d driven past these new stands of it on Wimberley’s River Road, knew it was invasive, but didn’t know how seriously invasive until my neighbors and fellow Hays County Master Naturalists Diane and Jerry Lunow suggested I check it out. As drier climate and increased well pumping in the Hill Country shallow out our streams, Arundo morphs from bank stabilizer to flow choker in a few seasons. It will change the look of the iconic streams we cherish. It will change nature.
Arundo was imported from the Mediterranean to the United States in the 1820s through California and widely cultivated. It’s used in making reeds for woodwind instruments—clarinets, oboes, bassoons—and unfortunately there isn't a native alternative. The giant reed has also been used for roof timbers, in basket making, for fishing rods, medicine, livestock fodder, and has been planted to prevent soil erosion. Nurseries still advertise it online. But in nature it’s a nightmare. Watch this video!
It has spread throughout temperate areas of North America, including most of Texas. The warming climate will only encourage spread.
Perhaps as penance, Californians have for decades poured money, research, and volunteer labor into unsuccessful, even dangerous, eradication attempts. We can learn from this one project. It’s agony.
From John Zentner and Daphna Huele, The Restoration Trust, 2020 [bolding and comments are mine]:
Cutting alone will not control giant reed. One stand, cut in the fall, grew back to its original height (about 16 ft) in 5 months. …Our efforts at control on the project sites consisted primarily of cutting and spraying the cut Arundo stumps with one application of a 41% solution of glyphosate (Roundup) [banned in Europe and Canada]. Alternative methods (foliar spraying, burning, digging) were not practicable due to the proximity of homes… Uh, and plant and animal life??
Based on our preliminary results, the way to minimize follow-up work on a stand of giant reed is to cut in the fall and spray the cut stump immediately after it is cut (within one to two minutes). …Site clearance was not cheap. The Council and the Trust opted to remove all invasive plants on the four sites treated in 2019 at a cost of about $2.00/sq. ft. …Restoration consisted of planting native grasses and sedges by community volunteers.
Arundo spreads [by thickly matted rhizomes (underground stems) and] by vegetative propagules. These propagules are typically parts of the plant that break off and are spread downstream… Arundo can also “layer” itself, as the descending tips of the plant take root in or near the original plant… Theoretically, then, if control begins in the upper watershed and moves downstream, one would have some hope that complete eradication could be reached on a watershed-by-watershed basis. [Roundup and propagules move right down the watershed, killing the wildlife, making way for the reeds!]
Arundo seems to exhibit a short period of dormancy in late fall; this appears to be the most effective time to cut and spray… [We] apply full strength glyphosate to the stump within one to two minutes after cutting. For large stands, we generally cut and remove the stalks, leaving a four to five-inch stump. We then re-cut that to a one- to two-inch stump and spray immediately, working behind the cutter (usually a metal-edged weed trimmer).
You feel their desperation. They also tried foliar spraying from helicopters directly onto large stands of reed. They tried imazapyr, another bio-toxic spray, “with highly variable effectiveness.” It gets worse:
Several alternative control treatments have been tested but have generally not been successful. Digging Arundo rhizomes out of the ground by hand is not usually feasible, even in sandy-soiled riparian habitats, due to the amount of effort required, high labor costs, and the negative impacts to adjacent plants and nearby wildlife (Hoshovsky 2003). Mechanical cutting or mowing of Arundo stalks has similar drawbacks (Wright 2015). Prescribed burning has been tried but is not practicable for urban or suburban areas with high fire susceptibility… Grazing has also been tried but has had limited applicability due to the height of the Arundo stalks [and their unpalatability]…
Arundo changes the landscapes it invades, mostly in negative ways. The dense stands provide less shade than the native trees that occupy the same habitat… Reduced shade causes warmer creek temperatures, resulting in increased algae growth and lower dissolved oxygen levels, leading to aquatic wildlife mortalities. Arundo also uses much more water than the native trees, sometimes three times as much, which reduces creek water levels during summer and fall. … Giant reed also sheds old stems, creating piles of dry grass that pose a significant fire hazard. …
So, until a reliable non-toxic eradication method for Arundo Giant Reed is available, prevention seems to be the best medicine. Now, in the fall and winter months, is the time to carefully eradicate isolated stands of this invasive giant grass before it goes monoculture in Central Texas river courses and impossibly out of control. Landowners, those of you blessed to be stewards of a Central Texas creek or river, talk with the Hays County Master Naturalist HELM folks about Giant Reed on your water. Talk with city and county leaders about public initiatives. And get local river restoration ideas with this amazing comprehensive resource from Texas Parks and Wildlife Department.
But if you’ve got any amount of Arundo Giant Reed on your water, find specific information you’ll need to control it before it destroys your stretch of stream! Read about it at Texas Parks and Wildlife Department’s Healthy Creeks Initiative to Combat Invasive Arundo.
From TPWD’s Healthy Creeks Initiative:
HOW CAN I PARTICIPATE? As part of the Healthy Creeks Initiative, we are offering no-cost Arundo control for landowner partners in our project areas. To participate, you’ll need to sign a landowner permission form to grant access for treatment and monitoring. You can terminate the agreement any time by email or letter, and you’ll always receive advance notice before our staff, partners, or contractors access your property.
To learn more, email healthycreeks@tpwd.texas.gov or reach out to your local contact:
For the Blanco & Little Blanco Rivers, your contact is Ryan McGillicuddy, ryan.mcgillicuddy@tpwd.texas.gov Phone: 512-552-3713
In Hays County, here’s what’s at stake—the dry white Blanco as the Spaniards named it…
A drought-thin but still beautiful Blanco in August morning light…
And when the rain returned, our dream of the Blanco on a quiet country night…
Our rivers are life. Protect them. Restore them.
Here’s your reward for reading this far! Watch this video on a big screen for that delicious vertigo of “really flying!” From Texas Parks and Wildlife Department and PBS television, it’s a thrilling aerial photography segment shot in 2013. Take a dizzying flight over our Texas rivers pre-drought!
From the air, try to spot the Giant Reed (Arundo). It was useful for bank retention during average to high flow on so many of our rivers. But recently, in drought, these stream courses have narrowed, facilitating an explosion of Giant Reed, which throttles already diminished stream flow and stifles aquatic life. Or just hold on and enjoy your flight!